Pipe flanges are typically a plate or ring that forms a rim at the end of a pipe for joining the pipe to another pipe or fitting. The flange typically has a series of bolt holes provided about its circumference to permit the pipe to be fastened at the joint. A flange joint refers to the connection of two pipes end to end, where the connecting pieces each have a flange by which the end of the pipes are bolted together. Typically a rubber gasket is provided between the faces of the adjoining flanges of a flange joint. It is important that the faces of the adjoining flanges be as smooth and flat as possible in order to ensure a proper seal at the joint.
A slip-on flange is typically connected to the end of the pipe by fillet welding around the circumference of the pipe where it meets the flange on both the inside and outside circumferences. On the inside circumference it is necessary to grind the weld back to the same inside diameter as the pipe. It may also be necessary to radius the inside edge of the welded region in order to provide a smooth transition from the inside of the pipe to the face of the flange, e.g. for rubber-lined pipes. The grinding and radiusing of the welded region around the inside diameter is labour-intensive and therefore expensive. It is also difficult to control the quality of the finish, so that the finished product may not be sufficiently smooth and/or flat.
Pipe flanges are manufactured in a variety of shapes and sizes according to various international standards. In mineral processing, oil and gas, chemical and water plants, steel pipe for carrying slurry and/or fluids and/or chemicals may be rubber-lined or ceramic-lined. With lined pipes it is important that the lining material also extend over the welded region to prevent any weakness or susceptibility to increased wear or corrosion in this region.
The present invention was developed with a view to providing a pipe flange that is easier to weld to the end of a pipe and that enables a better finish to be achieved. Although the invention is described with particular reference to a slip-on flange it will be apparent that the invention may also be applicable to other types of pipe flange, e.g. a lap joint flange.
References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.